hiatus semilunaris

The hiatus semilunaris (or semilunar hiatus) is a crescent-shaped groove in the lateral wall of the nasal cavity just inferior to the ethmoidal bulla.

The hiatus semilunaris is bounded inferiorly by the sharp concave margin of the uncinate process of the ethmoid bone, and leads into a curved channel, the infundibulum, bounded above by the bulla ethmoidalis and below by the lateral surface of the uncinate process of the ethmoid.